Several human conditions are characterized by distinctive lipid compositions of tissues, cells, membranes, and extracellular regions or structures. For example, in atherosclerosis, cholesterol (unesterified, esterified, and oxidized forms) and other lipids accumulate in cells and in extracellular areas of the arterial wall and elsewhere. These lipids have potentially harmful biologic effects, for example, by changing cellular functions, including gene expression, and by narrowing the vessel lumen, obstructing the flow of blood. Removal of these lipids would provide numerous substantial benefits. Moreover, cells, membranes, tissues, and extracellular structures will benefit in general from compositional alterations that include increasing resistance to oxidation and oxidative damage, such as by increasing the content and types of anti-oxidants, removing oxidized material, and increasing the content of material that is resistant to oxidation. In aging, cells have been shown to accumulate sphingomyelin and cholesterol, which alter cellular functions. These functions can be restored in vitro by removal of these lipids and replacement with phospholipid from liposomes. A major obstacle to performing similar lipid alterations in vivo has been disposition of the lipids mobilized from tissues, cells, extracellular areas, and membranes. Natural (e.g., high-density lipoproteins) and synthetic (e.g., small liposomes) particles that could mobilize peripheral tissue lipids have a substantial disadvantage: they deliver their lipids to the liver in a manner that disturbs hepatic cholesterol homeostasis, resulting in elevations in plasma concentrations of harmful lipoproteins, such as low-density lipoprotein (LDL), a major atherogenic lipoprotein. There exist a need for better methods to manipulate the lipid content and composition of peripheral tissues, cells, membranes, and extracellular regions in vivo.
The intravenous administration of cholesterol-poor phospholipid vesicles (liposomes) or other particles that transport cholesterol and other exchangeable material from lipoproteins and peripheral tissues, including atherosclerotic arterial lesions, to the liver produces substantial derangements of hepatic cholesterol homeostasis, such as enhanced hepatic secretion of apolipoprotein-B, and suppression of hepatic LDL receptors. The hepatic derangements lead to increase plasma concentrations of LDL and other atherogenic lipoproteins. Increased concentrations of LDL or other atherogenic lipoproteins will accelerate, not retard, the development of vascular complications. Deranged hepatic cholesterol homeostasis can also be manifested by abnormal regulation of genes, such as a gene for the LDL receptor, a gene for HMG-CoA reductase, a gene for cholesterol 7-alpha hydroxylase, and a gene regulating a function involved in cholesterol homeostasis. There exists a need for methods or compounds that can produce a removal of cholesterol and other exchangeable material, from peripheral cells, tissues, organs, and extracellular regions, and that can produce a delivery of material, such as phospholipids, to cells, tissues, or organs, extracellular regions, but without harmfully disrupting hepatic cholesterol homeostasis and plasma concentrations of atherogenic lipoproteins.
The invention described herein provides methods and compositions related to the removal of cholesterol and other exchangeable material from peripheral tissues, and otherwise altering peripheral tissue composition, while controlling plasma concentrations of LDL and other atherogenic lipoproteins and avoiding harmful disruptions of hepatic cholesterol homeostasis.
The present invention provides a pharmaceutical composition, kit, and method of forcing the reverse transport of cholesterol from peripheral tissues to the liver in vivo while controlling plasma LDL concentrations. The method includes the step of administering a therapeutically effective amount of a multiplicity of large liposomes comprised of phospholipids substantially free of sterol for a treatment period. The method optionally includes the step of periodically assaying plasma LDL concentrations with an assay during the treatment period to assess plasma atherogenic lipoprotein concentrations and obtain an atherogenic lipoprotein profile, and adjusting the administration in response to said profile. The large liposomes are dimensioned larger than fenestrations of an endothelial layer lining hepatic sinusoids in the liver so that the liposomes are too large to readily penetrate the fenestrations. The therapeutically effective amounts are in the range of about 10 mg to about 1600 mg phospholipid per kg body weight per dose. A pharmaceutical composition and related kit for mobilizing peripheral cholesterol and sphingomyelin that enters the liver of a subject consisting essentially of liposomes of a size and shape larger than fenestrations of an endothelial layer lining hepatic sinusoids in the liver is also provided.
It is an object of the present invention to provide a better method to manipulate the lipid content and composition of peripheral tissues, cells, membranes, and extracellular regions in vivo.
It is a further object of the invention to provide methods or compounds that can produce a removal of cholesterol and other exchangeable material, from peripheral cells, tissues, organs, and extracellular regions, and that can produce a delivery of material, such as phospholipids, to cells, tissues, or organs, extracellular regions, but without harmfully disrupting hepatic cholesterol homeostasis and plasma concentrations of atherogenic lipoproteins.
The objects and features of the present invention, other than those specifically set forth above, will become apparent in the detailed description of the invention set forth below.